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991.
J. M. P. Q. Delgado 《Heat and Mass Transfer》2008,44(12):1427-1434
The concentration distribution in the wake of a soluble sphere immersed in a granular bed of inert particles, through which
fluid flows with “uniform velocity”, has been obtained numerically, for solute transport by both advection and diffusion/dispersion.
Fluid flow in the granular bed around the sphere was assumed to follow Darcy’s law and, at each point, dispersion of solute
was considered in both the cross-stream and streamwise directions. The elliptic PDE equation, resulting from a differential
material balance on the solute, was solved numerically over a wide range of values of the relevant parameters (Peclet number
and Schmidt number). The solution gives the concentration contour plots and, for each concentration level, the width and downstream
length of the corresponding contour surface were determined. General expressions are presented to predict contaminant “plume”
size downstream of the polluting source. 相似文献
992.
993.
J.S. Valente P. Navarro J.J. Delgado E. Torres-García 《Applied Surface Science》2008,254(10):3006-3013
In the present work, a detailed study on structural and textural properties, as well as a thermo-kinetic characterization of two manganese cryptomelane-type oxides, was carried out. A suitable methodology was stated for determining the several stages taking place during the surface molecules’ removal. Thus, further insights were provided about the chemical nature of the sites present at the solid's surface. Relative strengths and the number of basic sites at the surface were estimated. The results show that the removal of the adsorbed (H2O, CO2) molecules from the surface is essential to disclose the oxide surface features. The morphological properties and thermo-kinetic characterization indicate the existence of at least three types of basic sites, owing activation energy values ranging from 140 to 190 kJ/mol. The dispersion observed in the activation energy data, during the CO2 loss, suggests that the interaction occurs on different sites. Therefore, both samples showed a heterogeneous surface; this is related to the energetic nature of the sites, as well as the basic strengths of the surface manganese cryptomelane oxides. 相似文献
994.
综合利用Leray-Schauder度理论的同伦不变性、上下解方法等,在符号型Nagumo条件下获得了一类三阶非线性常微分方程在非线性边界条件下解的存在性结果. 相似文献
995.
近几年来,人们采用各种方法试图将1D隐马氏模型(HMM)^[2]推广到2D隐马氏模型。令人失望的是由于在建立合适的2D模型及其计算上的复杂度问题上存在困难,前面的尝试都没有得到一个真实的2DHMM.本文对于应用真实2D隐马氏模型(隐马氏网格随机场HMMRF)^[1,4]进行手写字符识别问题提出新的框架,针对文献[1]中的单点最优算法给出局部最优的译码算法。HMMRF模型是1D隐马氏模型到2D的扩展,能更好的描述字符的2D特性。HMMRF在字符识别中的应用具有两个相——学习相和译码相。在学习相和译码相中我们的最优标准是基于极大边缘后验概率的。不过,在涉及到2D模型中的计算问题时,对模型做出某些简单化的假设是必要的。本文用到的方法对于在合理的模型假设下解决手写字符识别问题呈现了很大的潜力。 相似文献
996.
997.
R.M. Durán Delgado G. Gustafson L. Lönnblad 《The European Physical Journal C - Particles and Fields》2007,52(1):113-119
We investigate some recent measurements of Fermi–Dirac correlations by the LEP collaborations indicating surprisingly small
source radii for the production of baryons in e+e- annihilation at the Z0 peak. In hadronization models there is besides the Fermi–Dirac correlation effect also a strong dynamical (anti-) correlation.
We demonstrate that the extraction of the pure FD effect is highly dependent on a realistic Monte Carlo event generator, both
for separation of those dynamical correlations that are not related to Fermi–Dirac statistics, and for corrections of the
data and background subtractions. Although the model can be tuned to well reproduce single particle distributions, there are
large model uncertainties when it comes to correlations between identical baryons. We therefore, unfortunately, have to conclude
that it is at present not possible to draw any firm conclusion about the source radii relevant for baryon production at LEP.
PACS 13.60.Rj; 13.66.Bc 相似文献
998.
999.
A New Quantum Secure Direct Communication Protocol Using Decoherence-Free Subspace 总被引:1,自引:0,他引:1 下载免费PDF全文
A new quantum secure direct communication (QSDC) protocol is proposed by using decoherence free subspace (DFS) to avoid insecurity of the present QSDC protocols in a quantum noise channel. This protocol makes it easily for Bob and Alice to find eavesdropping in channel because the collective dephasing noise disappears in DFS. The probability of successful attack by Eve in this protocol is smaller than in BB84 protocol. Thus this protocol realizes secure QSDC and is feasible with present-day technology. 相似文献
1000.
半色调彩色图像的反射率模型 总被引:1,自引:0,他引:1
光在纸张与油墨内散射或油墨在纸基内渗透都将影响半色调印刷图像的阶调特性.考虑到油墨在纸面上扩展所形成的墨点非矩形特性、光在纸基内传播的多次散射性和油墨在纸基内的渗透作用,采用纸张与油墨反射率与透射率的迭代修整方法建立了印刷图像的反射率新模型.理论模型中用纸张与油墨的反射率是油墨网点面积率的函数和实验参量砌描述纸张和油墨对反射模型的影响. 相似文献